The invention is in the field of electro-optical devices and in particular is useful for image intensifiers. Such intensifiers usually include a photocathode onto which a visible-light image to be intensified is projected. The photocathode produces an electron image, and this electron image is focussed onto a microchannel plate (MCP) which functions as an electron multiplier. The MCP thus produces a multiplier electron image of the visible-light image. The electrons of the multiplied electron image are drawn by a high voltage to a phosphor to produce a visible image that is an intensified representation of the original visible-light image. An example of such an intensifier is shown and described in an article in Electronics of Sept. 27, 1973, pages 117-124. Alternatively, an earlier embodiment (first generation) of image intensifier included no MCP, but focussed the electron image from its photocathode directly onto an output phosphor. An example of such an intensifier is U.S. Pat. No. 3,280,356 of Oct. 18, 1966. Third generation image intensifiers now being developed use neither an MCP nor a focussing electrode, but each has an output phosphor screen closely adjacent and parallel to a photocathode. With any of these three types of intensifiers, the problem exists of internal reflections within the intensifiers. Such reflections may arise from the usual aluminum layer on the output phosphor or from other internal structures of the intensifiers, such as MCPs or focussing electrodes. The radiation being reflected is that which penetrates the photocathode from the (unintensified) light image side. Such radiation may be reflected back to the photocathode and cause spurious outputs of electron therefrom. Reflections from the aluminum layer on the output phosphor may be eliminated by covering the aluminum with black antihalation coatings such as black nickel, gold, carbon, or some mixtures of carbon and metallic blacks. However, such coatings have two disadvantages. First, in order to adequately absorb incident radiation, the coatings must be relatively thick; however, a thick coating has poor electron transmissivity. Second, such coatings do not adhere well to the aluminum layer on the phosphor. Another way of eliminating reflections uses several layers of a dielectric material. As with the black antihalation layers, such layers have the disadvantages of poor electron transmissivity. Moreover, the problem of charging of the dielectric exists. Such charging adversely affects device life, and, in severe cases, may cause voltage breakdown. Further, the thickness of such layers seems to be responsible for gain reductions and noise figure increases in devices so coated. The instant invention is able to provide a thin, non-charging coating relatively transparent to electrons but opaque and absorbing for undesired electromagnetic radiations.